Screw mechanism



April 16, 1940.

R. M. NARDQNE SCREW MECHANISM Filed Sept. 10, 19258 2 Sheets-Sheet lKik..

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April 16, 1940. R. M. NARDONE scREw MEcHANIsu Filed sept. 10. 19s8'f 2Snets-sheet 2 Imm! INVENTOR NEY.

tl', I IIII Patented Apr. 16,

UNITED STATES PATENT OFFICE i `2,197,155 .I 'l n SCREW MECHANISMltomeo-M. Nardone, East Orange, N. J., assignor to Bendix AviationCorporation, South Bend, Ind.; a corporation of Delaware v i* lApplication September 10, 1938, Serial No. 229,376` y i s claims. (ci.'a4-459) This invention relates to driving mechanism, and moreparticularly to driving mechanism of the class employing substantiallyfrictionless rollers-balls, cylinders, or other rollers having curvedrolling surfaces-in positions intermediate the driving and drivenelements, for transfer of the drive from one to the other, inconjunction with a retaining cage or cages for said rollers.

An object of the invention is to provide novel means engageable withcertain of the rollers to absorb thrust, facilitate free rolling,. andlimit axial movement of the roller assembly, particularly in caseswherein the roller assembly is interposed between driving and drivenelements ll adapted to translate longitudinal motion to rectilinearmotion, or vice versa.

These and other objects of the invention will become apparent frominspection of the following specification when read with reference tothe acn companyingdrawings wherein is illustrated the preferredembodiment of the invention. It is to be expressly understood, however,that the drawings are for the purpose of illustration only, and are notdesigned as a deiinition of the limits s of the invention, referencebeing had to the appended claims for this purpose.

In the drawings,

Fig. 1 is a longitudinal sectional view of the invention as applied toscrew mechanism for .0 starting an internal combustion engine, thestarting mechanism shown being that which is dis- ;'closed and claimedin my application No. 100,000 filed September 9, 1936, now patent No.2,144,196 granted January 17, 1939;

Fig. 2 is a transverse sectional view along the line 2-2 of Fig. 1;

Fig. 3 is a side elevational view of an element of the assembly of Fig.l;

Fig. 4 is a longitudinal sectional view of certain 0 of the parts ofFig. l, butin different relative 'postions;

Fig. 5 is a detail view of the cage balls and stops assembly on anenlarged scale;

Fig. 6 is a longitudinal sectional view of a 45 portion of the motiontranslating means of Fig. 1, incorporating therein a modifiedarrangement for retaining and controlling the action of the m0- iionfacilitating ball elements carried by said motion translating means;

50 Fig. '7 is a'transverse section along the line 1-1 of Fig. 6;

Fig. 8 is an exploded perspective view of the inner cag: innon-assembled relation to certain ofthe driving elements; and

55 Flgs..9 to 12, inclusive, are diagrams illustrating 4successivestages of theroller and cage assem? bly process, for the embodiment ofFig. 6. l

With reference to the drawings, and more 'particularly to Fig. 1, thescrew mechanism is contained within a sectional housing including cylin-5 drical parts l1 and i0, the latter having a flange i2 by which it issecured tor an engine crankcase i3 as by bolts Il, the flange beingconveniently of a size standardizedfor aircraft engine starters. Theengine crankshaft, or other drive shaft l0 (not shown) is provided witha clutch-element I I engageable by the piston actuated clutch-element`i5 as will be later more fully described.

Cylinder I1 has a head end I3 and a crank end 20, the latter beingshownas an integral ll part of a splined tube 2l. Slidably fitted withinthe cylinder I1 is a piston 23 movable with a hollow internally andhelically grooved screw 24 which is externally splined as at 25, tocooperate with the internally splined tube 2 I. Between the mcooperating grooves 25 and 26 are placed a series of friction reducingmembers shown as balls 21 assembled in a cylindrical cage a (Fig. 5),the end rows of balls having their surfaces engageable with plates 28located at each end of the 25 splined grooves to facilitatefree rollingmovement of the balls which they engage at points spaced above or belowthe mid-plane thereof, and also to hold thecage 30a against more' than apredetermined e'ndwise movement. A'second 30 screw 22 is drivablyconnected with the screw 2l by helical grooves or threads 29 and 30which permit the axial travel of the piston 23 but cause rotation of thescrew 22 because of friction reducing balls 36 inserted in the helicalgrooves 35 29 and 30. An anti-friction thrust bearing 32 is preferablyinterposed between a flanged skirt 34 on rear end of spacer 34a and aninwardly extending circular rim 33 of the cylindrical part I0. Theinwardly extending rim 34h on the forward 40 end of spacer 34a takes thethrust as jaw i5"` rides into mesh with engine member ii. A spring 31has one end resting against the closure plate 2li of the cylinder i1,and its opposite end abuts the thrust ring 38, which is, in effect, theouter race of a ball bearing assembly i0 axially movable with butrotatably free of the piston 23, the intervening bearing balls 40facilitating free rotation of outer race 38 of the bearing, the outerrace being possibly constrained to rotation by the natural twistingtendency of a spring such *as the spring 31, as the latter is compressedin'the forward travel of the piston. Piston rings, insure against theloss of pressure as the piston moves forward, and also yieldably opposerotation a vio 2 arcaica haust connection 4i leading to any desiredpoint.

In the case of an airplane. for example, this exhaust connection willlead to a point exteriorly of the fuselage. 'I'he valve 42 is carried bya stem ll whichis of such a length that with the piston' in its positionas indicated in Figure l. a spring Il will bear against an enlarged headI! on the stem 4l to hold valve Il closed. At the commencement of anoperative cycle of the motor, such asis occasioned by the delivery offluid pressure to the chamber formed by the neckportion I8 oi' thehousing Il, this fluid pressure will act upon the head portion of thevalve insuchmannerastoassistthespringin maintaining `the said exhaustvalve l2 allied:

but as the piston nearly reaches the end of its zmovement. a collarextending inwardly of piston 2l and surrounding the stem will be broughtinto engagement with the head l2 and, will be edective to unseat theexhaust valve 42. 'I'he exhaust valve having been unseated in the mannerdescribed, the spring 48 will be en'ective for holding it in openposition, its maximum opening movement being limited by a longitudiynally slotted cylindrical stop Il having a flange t8 abutting the endsurfaces oi' the nngers Il (shown in transverse section of Fig. 2)formed by longitudinally slotting the neck portion Il of the housing I8.I'his neck-portion 8l is externally.

threaded, as shown at n, to receive the housing M. the latter beingscrewed up on the threads 68 until surface I0 of the housing u abutsthe.

flange B6 of the stop N and with the inlet passage lia aligned with thelongitudinal slots between ilngers 81. Stop u is adapted-to be firstslipped over the valve head 42: and due to the eccentricity (indicatedat Il in Fig. 2) of the apertured portion of the base 'Il of the saidstop, the said base has suiilcient surface remaining to constitute a'stop or abutment for valve head l2 in the open position of the latter,while at the same time being apertured suiiiciently to permit insertionand withdrawal over said valve head.

'I'he piston having completed its operative stroke. and the exhaustvalve having been opened. the piston will be urged on its return strokeby the coil spring Il. During this return movement, the exhaust valvebeing held open, the cylinder will be effectively scavenged.' Due to theaction of the spring the valve will remain open until such time as thepiston odiar Il is brought to bear against the valve stem 41 for againseating the valve. This insures closing movement of the valve at thetime the piston has substantially completed its return movement. the

closing being initiated and assisted by the action of the spring meansl! above described. There is thus provided automatically controlledexhaust means, which exhaust means is of such construction as to remainopen during the maior portion of the return stroke of the piston so asto insure substantially complete scavenging.

"15." By reason of the action oi' sprinpm nu,

Il `and Il upon grooves Il and Il. respectively in sleeve 22.' theinitial axial movement of the piston 28 will be transmitted toeaidsleeve l2, and theaxialthrustthusimparted toiaw Il (through the flangeI! on sleeve l!) will establish engage I ment with the engine member Il.Upon such engagement the resulting resistance to further i axial travelwill cause, nrst, al commencement of rotation on the part of sleeve 22,and secondly, a slipping of the balls Il and Il from the grooves il)v f4Il and Il, so that they may be free to ride along the inner bore of thesleeve 21 as the piston continues forward; the furthest forward relativeposition of the balls "and Il being as indicated In order to assurealignment between the longitudinal slots IIb in the thimble shaped stopIl, and those'slots I'Ia formed by the lingers i1 of the neck portionIl, iiat surfaces Ma are provided on the :nimble shaped stop (asindicated in both 1 vFigures2itndli)toreg'isterwithcorresponding.-

flat surfaces lia on neck portion il. Thus there -is established adirect path for the pressure fluid entering the housing, said path beingin the form or a plurality orparsnel passages straight c through thelower halves ,of the slotted cylindrical walls of neck portion `It andthimble shaped stop Il, the said parallel passages being sumcientlynumerous and wide to allow entry of 'all the non-solid part of thecharge, while narx 0.

row .enough to block entry of any solid (unburned) pellets or particlesof explosive material from which the pressure iluid may be generated.

If the entering fluid attains an' excessive preesure orvelocity,'suilicient to carry it `thro'ugh o5 the upper slotted sectionsoi' thimble shaped stop I4 and neck` portion Il, with such abnormalforce as to rupture the protective disc l0, the

'breaking oi' said disc .will permit the escape to I the atmosphere, byway of outlet of such excess pressure, thereby protecting the otherparts of the device against derangement; but normally the advance ofpiston 2l (in response to the entry of the nuid into the chamber formedby the neck-portion it) will be rapid enough i to prevent accumulationof excess pressure in the crescent shaped region 'la immediately abovethe neck-portion 56. This region 1l is formed by making the innersurface of housing Il elliptical in cross-section, atthe parts (1l and11) 50 above and below the threaded regions (13 and 14) of contact withthe threaded surfaces 'Il of the neck-portion Il. This has the addedadvantage of providing a greater 'width of inlet space at region 1l(Fig. 2), making it possible 55 to' utilize all of the parallelpassagesforlned by fingers l1.

In the arrangement shown in Fig. 6 retainer rings 2l, Il and II aresecured 'to the ends of elements 2|, 24 and 22, respectively, and engage$0 the end rows of the balls 21V and 3l in tangential fashion ratherthan the edges of the cages, so that theytend to insure free rolling ofthe said balls, where otherwise there mightbe a binding or wedgingtendency-as, for example, if the ,65 retainer surfaces engaged the ballsat points in the surface of a cone passing through the centers of saidballs, with its apex on the llongitudinal axis of the sleeves Il, 24 and22.

To vassemble the Darts. I ilrst stand the sleeve 70 .Il on end, as bestshown in Fig. 8, and after placing cage l2 and retainer ring ll over theshaft of sleeve 24. With the parts in this position I then proceed toinsert balls 88 in the said lowest row 81 of openings, the said openingsbeing sui!!- ciently exposed to permit such insertion, and the concavesurfaces of the threads 88 at the upper end of sleeve 24 form shouldersto prevent dropping out of the balls during the process oi illling thisrow of holes 81. When the openings in row 81 have been thus illled, vIapply pressure on the shaft 22 to move it down, in relation to vsleeve24, a distance corresponding to the distance between transverse rows(the distance indicated at din Fig. 8). I then proceed to rlll the row88 with balls, and the concave surfaces of the threads 38 at the upperend of sleeve 24 again aid in the retention of the balls againstdropping out during this step in the process. These steps offllling onetransverse row at a time, then telescoping the inner shaft or sleeve 22to an extent equal to the distance between rows, are repeated, until thecage has been completely illled with balls, as shown in Figs. 6 and 1,and completely telescoped within the sleeve 24. Retainer ring 84 is thensecured over the end oi sleeve 24, the lip 88 of said retainer ringbeing registrable with an undercut recess in the splines 28 of thesleeve. The assembled shaft and sleeve are then inverted and placedabove the outer sleeve 2 I, the latter standing on end on a suitablesupport.` Gage 8| is then slid over the end of sleeve 24, down to thepoint where the lowest row of openings therein will be adjacent theplane of the end of the sleeve 24, as shown in Fig. 9. I then proceed tofill the rows with balls 21, one row at a time, with each successivestep of row lling separated by a step of telescoping the sleeves 24, 2lto an extent equal to the distance d' between successive rows, in otherwords, a repetition of the steps followed in assembling the parts 22, 82and 24, as previously describedthe successive steps being indicated inFigs. 10, 11 and 12. When this has been completed, re-

tainer ring 28 is secured in place to complete the entire assembly. v

What is claimed is:

1. The combination with two cylindrical drive transmitting parts, of acylindrical roller retaining cage interposed therebetween, a pluralityof rollers in said cage, and a retainer plate secured to one of saiddrive transmitting parts, said plate having a surface engageable withpoints on said rollers which are on parallel lines each of which passesthrough the center of onel of said rollers, and each of which passesthrough the cylindrical wall of said cage.

2. The combination with two cylindrical drive transmitting parts, of acylindrical roller retaining cage interposed therebetween, a pluralityof rollers in said cage, and a retainer plate secured to one of saiddrive transmitting parts, said plate having a surface engageable withsaid rollers tangentially thereto.

3. The combination with two cylindrical drive transmitting parts, of acylindrical roller retaining cage interposed therebetween, a pluralityof rollers in said cage, and a retainer plate distinct from said cageand secured to one of said drive transmitting parts, said plate having asurface engageable with said rollers to limit the motion of said cage inrelation to said drive transmitting parts.

ROMEOl M. NARDONE.

